Pneumatic tire



@wm 14? 1943 A. w. BULL ETAL 2,329,332

PNEUMATIC T 'IRE Filed Dec. '51, 1940I n i/gel?. 5

INVENTOR ARTHUR W. BULL GLENN G.HAVENS BY J'OHN F WILL/AMS ATTFNEYPatented Sept. 14, 1943 PNEUMATIC TIRE Arthur W. Bull, Grosse Pointe,Glenn G. Havens, Detroit, and John F. Williams, Grosse Pointe, Mich.,assignors to United States Rubber Company, New York, N. Y., acorporation of New Jersey Application December 31, 1940, Serial No.372,544

7 Claims. (Cl. 152--330) This invention relates to pneumatic tires andin particular, to pneumatic tires having electri-v rhigher speeds,quieter operation, and because the tires possess higher insulatingcharacteristics. Among the objectionable features of the accumulationand discharge of static in automotive vehicles are annoyance of shock topassengers when touching the vehicle shortly after it comes to a stop,and radio interference. Another objectionable feature is the occurrenceof sparks within the tire structure, resulting in the generation ofozone which is a detrimental iniluence associated with pneumatic tires.

In the practice of our invention, we have found a simple and efficientmethod of providing a path from the tire lrim to the ground ythroughwhich static may be discharged from 'the tire` This method consistsLgenerally of placing a thin ribbon of electrically conducting rubber`composition transversely on the outer surface of the tire carcass andunderneath the tread and sidewall rubber composition. In addition, asimilar strip extends circumferentially of the tire between the carcassandthe tread and contacts with the transverse strip.

It is recognized that the rubber composition of a pneumatic tire may bemade conducting by incorporating in the rubber compound a suflicientquantity of electrically conducting carbon black; however, thepresencein a rubber compound oi a sufcient quantity of electrically conductingcarbon black to render the composition adequately conductive produces acomposition of inferior physical characteristics, such as poor abrasionresistance and the like. Incorporating ribbons of conducting rubbercomposition in a tire, according to the practice of our invention, hasnot been found to detract in any way from the high quality of tireperformance.

Among the objects of our invention are to provide a pneumatic tire whichincorporates a conducting path for discharging static electricity; toprovide an efficient and economical method of obtaining an electricallyconducting path in a tire; to provide a conducting path in a tire whichdoes not interfere with the qual/ity of the tire; to reduce orelimina/te tube cracking due to the formation of ozone caused by anelectrical static discharge; to eliminate static shoc'r` 'from automotive vehicles; and to improve radio perform ance. These and otherobjects and advantages appear more fully in the following detaileddescription when considered in connection with the accompanying drawing,in which:

Fig. 1 is a side elevational view of a pneumatic tire assembly embodyingthe features of our invention; y

Fig. 2 is an enlarged transverse view thereof, in section, taken alongsection line lI-II of Fig. l;

Fig. 3 is a perspective view, in section, of a portion of a tread slabprior to its assembly 'with a tire carcass;

Fig. 4 is a perspective view, in section, of a A portion of a tread slabillustrating a modified form of the invention; and

Fig. 5 is a transverse View, in section, of nortion of a 'pneumatic tireand rim and illustrat ing a further modication of the invention.

With reference to the drawing and, in particular, to Figs, l and 2, weshow a pneumatic tire I0, which, in most respects, is similar to a conn1ventional pneumatic tire. The tire I0 includes a rubberized fabriccarcass I I, inextensible beads I2 and I3, a tread I4 of rubbercomposition, and sidewall portions I5 and I6 also of rubber composition.The tire I0 is illustrated in mounted position. on a drop center rim Iland with an inner tube I8 assembled Within the tire casing. Aconventional valve stem I9, communicates with the inner tube I8. The rimI'I, being formed of metal and associated directly or indirectly withthe various other metallic components oi an automotive vehicle, formsthe nearest direct, metallic, electrically conducting path to theground.

In order to decreasel the conducting distance from the rim to theground, we incorporate in the tire, between the tire carcass I I and itstread I4 and sidewall portions I5 and I6, a strip or ribbon 2n of rubbercomposition compounded to render it electrically conducting. This ribbon2li extends transversely of the tire so as to engage Parts by weight 100ne carbon black 50 addition to the ribbon 20, a second ribbon betweenthe tread i4 and the carc* the crown region of the tire andexcuznierentiaily c; `und the entire psiii- Ithis strip 23 rseiyextending in cross sectional rial composition is the By the combinationof electrically conducting on the flanges of the tire rim entirecircumference of underneath the tread, While this does not provide adirect electroni the rim to the ground ce of the it has been found 'iocause retention of an .tic charge in the automotive vehicle. e, theelectrical resistance of the e convention tread such as the disthecircumferential strip 23 to the outer sur ace o' the tread H can be madeless out 1,000 megohrns, whereas in a coni/'entional tire the resistancefrom the tire rim to the around usually exceeds 10,000 niegobm...luoghi() rnego'nrns. Such a conducting extending from the tire rirn tothe underne tread ii provides a sufficient means li that a car willdischarge the accumulated tic by the time it is brought to a stop, itthe ce time the conducting path acts a proniedium or shield whichprevents or try reduces the detrimental influence of lis or on the tirecarcass. conducting ribbon 2E, extending transf the tire, may be u edalone or in coi extending ung stl p 2li is 'e will discharge at theingest rate brings the strip into close proxground or tire supportingsur- .se discharge oi static will be been obtained by this villen treadsof exceptionally ical res'stence are used, because the strips providedon each of the four automotive vehicle will, on an average, ated in suchdifferent positions that the` once during the complete revolution of aThe addition of the circumferential not ever, should be made for treadsoi" c ectricel resistance. Addition of this strip overcomes the periodicdischarge condition, effecting a uniform and higher average rate ofdischarge.

Referring to Fig. 3, We show a tread slab 2| in its extruded shape priorto its application to a pneumatic tire. After the tread slab 24 isassembled with the tire and the tire is vulcanized, the tread slab isformed into a tire cover such as represented by the tread I4 andsidewall portions |5 and I6 of Fig. 2. While the tread is in slab iorm,as shown in Fig. 3, and after the strip 23 is applied to the tread slab,the strip 20 is easily and quickly applied to the top surface of theslab, the top surface being the surface which lies adjacent the tirecarcass Il. Both the tread slab 2l and the conducting strip 20 are intheir unvulcanized state when assembled; therefore, no cementing orother bonding operation is required. It is merely necessary to place thestrip in a substantially transverse position in relation to the treadslab to which it will readily adhere. Thereafter all of the tirebuilding opereticns are in accordance with conventional practice and thethin strip 20 in no Way interferes with subsequent operations. In orderto insure proper Contact of the transverse strip 2D with the flanges ofa tire rim, one or both ends of the strip may be bent around the edge ofthe tread slab. For example1 portion 25 of the strip 20 may be bentaround the edge of `the sidextei portion i5 of the slab so that theportion lies on the opposite side 0f the tread slab. in Fig. 2, theover-lapped portion 25 lies in a position to make a good Contact uflange 2| of the rim i1.

As sho in Fis. 3, the circumferential strip 23 is anni d to the topsurface of the tread slab 24 wn e it is in an unvulcanized state andprior to assembly with the tire carcass. The strip 23 may applied to thetread in a separate operation or it may be extruded simultaneously withthe tread in a conventional dual extrusion method.

Fig. 4 illustrates s. niodicaiion of the invention, showing a, treadslab 26 with which is assembled a single transversely extending strip 21oi electrically7 conducting rubber composition. This inodication merelyshows that a transverse conducting strip may be used alone, that withoutas...ciation or contact with a circum- `ierentially extending strip. Themodification also shows that while it is preferable, it is not necessaryto bend the end of the strip around the marginal edge of the tread slab.A tire having a tread slab and transverse strip, such as shown in Fig.4, embodied in a tire assembly will correspond substantially to theright hand portion oi the tire assembly shown in Fig. 2; thecircumferentially extending strip 23 having been omitted therefrom.

A further modiiication of the invention is illustrated in Fig. 5, whichshows a portion of a tire carcass 28, an inextensible bead element 29,and sidewall rubber composition 30. A portion only of the tire is shownmounted on a rim 3l provided with a flange 32. An electrically con`ducting, transversely extending strip 33 is interposed between thesidewall 30 and carcass 28 and follows the general assembly constructionshown in the modification in Fig. 4. The only additional elementincluded in Fig. 5 is the use oi a fabric chang strip 34. tire buildingpractices it is customary to add a chang strip of fabric to the outsideof the tire bead portions as a protection to the tire bead Inconventionalvgood conducting path is formed between fabric from abrasionwhich might result from its engagement with the tire rim flanges.Chafing strips are usually frictioned or otherwise coated with a rubbercomposition. In the practice of our invention, we provide a chaflngstrip 34 which is frictioned or coated with an electrically conductingrubber composition. The rubber composition employed in coating thechafing strip contains a relatively high per cent. of conducting carbonblack such as acetylene carbon black. The conducting chafer insures anelectrical contact with the rim flange throughout the life of the tire.The chaflng strip 34 is applied to and forms a part of the carcass 28.Thereafter, as the tread is applied, the sidewall portion 30 overlapsthe chaflng strip 34 in part. The transversely extending conductingstrip 33 lying on the inner surface of the tread wall 30 becomes firmlyassociated with the chaflng strip 14. Thus, as the chailng strip lies incontacting engagement with the flange 32 of the rim 3|, a the rim 3l andthe conducting strip 33.

From the foregoing description it is believed apparent that 'we haveprovided a novel and efflcient method of forming a conducting path inpneumatic tires for the discharge of static electricity, and while wehave shown and described a preferred embodiment of our invention, it isto be understood that it is susceptible of modiflcations as appearingwithin the spirit of the invention and the scope of the appendedclaims.`

Having thus shown and described the invention, what we claim and desireto protect by Letters Patent is:

1. A pneumatic tire comprising a carcass f strain resisting elements, atread and sidewall portions of rubber compositionya ribbon ofelectrically conducting rubber composition not more than severalhundredths of an inch thick lying between the carcass and the tread andsidewall portions so that it is completely covered for the major portionof its length, the ends of said ribbon terminating at opposite beadregions of the tire, to thereby provide an electrical path from the beadportion to the tread portion of the tire. 1

2. A pneumatic tire comprising a carcass of strain resisting elements, atread and sidewall portions of rubber composition, a ribbon ofelectrically conducting rubber composition not more than severalhundredths of an inch thick lying between the carcass and the tread andsidewa l l portions so that it is completely covered for the majorportion of its length, the ends of said ribbon terminating at oppositebead regions of the tire, one end portion of said ribbon being foldedaround the marginal edge of one of the sidewall portions, to therebyprovide an electrical path from the bead portion to the tread portion ofthe tire.

3. A pneumatic tire comprising a carcass of strain resisting elements, atread and sidewall portions of rubber composition, a ribbon ofelectrically conducting rubber composition not more than severalhundredths of an inch thick lying between the carcass and the tread andsidewall portions and extending circumferentially of the tire at thecrown portion thereof, and a transversely extending ribbon ofelectrically conducting rubber composition disposed between theferentially extending ribbon andterminating at the bead region of thetire, to thereby provide an electrical path from the bead portion to thetread portion of the tire.

4. A pneumatic tire comprising a carcass of strain resisting elements, atread and sidewall portions of rubber composition, a ribbon ofelectrically conducting rubber composition not more than severalhundredths of an inch thick lying between the carcass and the tread andsidewall portions and extending circumferentially of the tire at thecrown portion thereof, a transversely extending ribbon of electricallyconducting rub ber composition disposed between the carcass and sidewallportion so that it is covered by the latter and contacting with thecircumferentially extending ribbon land terminating at the bead regionof the tire, an end portion of said transversely extending ribbon beingfolded around the marginal edge of one of the side wall portions, tothereby provide an electrical path from the bead portion to the treadportion of the tire.

5. A pneumatic tire comprising a carcass of strain resisting elements, atread and sidewall portions of rubber composition, a chang strip offabric rubberized by the application of an electrically conductingrubber composition, a rib- Y bon of electrically conducting rubbercomposiby the latter and contacting with the circumtion not more thanseveral hundredths of an inch thick Alying between thefcarcass and thetread and sidewall portions so that it is completely covered for themajor portion of its length, the ends of said ribbon terminating atopposite bead regions of the tire in contact engagement with saidchaflng strip, to thereby provide an electrical path from the beadportion to the tread portion of the tire.

6. A pneumatic tire comprising ,a carcass of strain resisting elements,a tread and sidewall portions of rubber composition, a chailng strip offabric rubberized by the application of an electrically conductingrubber composition, a ribbon of electrically conducting rubber composition not more than several hundredths "of an inch thick lying betweenthe carcass and the tread and sidewall portions and extending ciri-vcumferentially of the tire at the crown portion thereof, a transverselyextending ribbon of electrically conducting rubber composition disposed.

between the carcass and sidewall portion so that it is covered by thelatter and contacting with the circumferentially extending ribbon andterminating at the bead region of the tire in contact engagement withsaid chafing strip.

'7. A pneumatic tire comprising a carcassbf strain resisting elements, atread and sidewall portions of rubber composition, a chailng strip offabric rubberized by the application of an electrically conductingrubber composition, a ribbon of electrically conducting rubbercomposition not more than several hundredths of an inch thick lyingbetween the carcass and the tread and sidewall portions so that it iscompletely covered for the major portion of its length, the ends of saidribbon terminating at opposite bead regions of the tire in contactengagement with said chafing strip, an end portion of said transverselyextending ribbon being folded arund the marginal edge of one of thesidewall portions.

ARTHUR W. BULL. GLENN G. HAVENS. JOHN F. WIILIAMS.

